1. Field of the Invention
The present invention relates to semiconductor devices, in particular to micro- or millimeterwave devices, embedded in an interconnect platform and manufacturing methods thereof.
2. Background of the Invention
The increasing usage of MMIC""s (Monolithic Millimeterwave Integrated Circuit) in application fields such as the automotive industry is a strong driving force to develop alternative technologies with equal performance level but at lower cost. In standard MMIC technology the active element and the passive circuitry are formed in a monolithic way on a single substrate. This substrate must fulfil all the requirements with respect to e.g. the growth of semiconductor layers, high frequency performance, manufacturability and cost. An alternative technology is the hybrid integration of individual HEMT""s (High Electron Mobility Transistor) with passive circuitry on low-cost substrates. In this way, the epitaxial area consumption per chip can be reduced dramatically.
In U.S. Pat. No. 5,675,295, hereby incorporated by reference, a microwave oscillator device for a receiver or a transmitter is described. This oscillator device comprises a high frequency oscillating circuit including an active device. The active device, i.e. a vertical diode, is formed on an undoped, semi-insulating, GaAs substrate. This manufacturing method comprises the steps of depositing a sacrificial layer on this GaAs substrate, followed by the deposition on this sacrificial layer and subsequent patterning of the layers, e.g. semiconductor layers, which compose the active device. An example of a manufacturing method of such active elements can be found in xe2x80x9cW-band high-gain amplifier using InP dual-gate HEMT technologyxe2x80x9d, by K. van der Zanden et al, in Proc. InP and related Materials, 1pp7, pp249-252, hereby incorporated by reference. The thus formed vertical active device (see FIG. 1b) is then separated from the undoped GaAs substrate e.g. by applying the epitaxial lift-off (ELO) technique wherein the sacrificial layer, sandwiched between the active device and the semi-insulating substrate, is selectively etched. After separation the active device is transferred to and attached on a second substrate. This second substrate can be any other substrate, comprising passive circuitry and interconnects.
One aspect of the invention is directed to providing high frequency devices comprising at least one semiconductor element interconnected to a passive circuitry. Thus, a preferred embodiment provides a method of fabricating a semiconductor device, comprising depositing two or more layers of semiconducting material onto a first substrate to form a first semiconductor stack, singulating said first semiconductor stack to form a first group of singulated semiconductor stacks, wherein said first group is comprised of at least a first singulated semiconductor stack having a top semiconducting layer, a bottom first substrate layer, and an inner semiconducting layer in contact with said bottom first substrate layer, providing a second substrate having a first conductive layer and a first bonding material deposited thereon, selecting said first singulated semiconductor stack from said first group, attaching said upper semiconducting layer of said first singulated semiconductor stack to said conductive layer to form a second semiconductor stack, and removing said two or more layers of semiconducting material in said second semiconductor stack from said first substrate layer to thereby form a semiconducting device in which said inner semiconducting layer is exposed. In a further preferred embodiment, a tandem cell cell is provided by employing as the second substrate a semiconductor having a band gap that is different from the band gap of said second semiconductor stack.
In another preferred embodiment, a method fo fabricating a semiconductor device is provided, comprising depositing a sacrificial layer onto a first substrate, depositing two or more layers of semiconducting material onto said sacrificial layer to form a first semiconductor stack, singulating said first semiconductor stack to form a first group of singulated semiconductor stacks, wherein said first group is comprised of at least a first singulated semiconductor stack having a top semiconducting layer, a bottom first substrate layer, and an inner semiconducting layer in contact with said bottom first substrate layer, providing a second substrate having a first conductive layer and a first bonding material deposited thereon, selecting said first singulated semiconductor stack from said first group, attaching said upper semiconducting layer of said first singulated semiconductor stack to said conductive layer to form a second semiconductor stack, and removing said two or more layers of semiconducting material in said second semiconductor stack from said first substrate layer to thereby form a semiconducting device in which said inner semiconducting layer is exposed.
Another aspect of the invention is directed to providing a manufacturing method for hybrid integration of individual semiconductor devices with passive circuitry. A preferred embodiment thus provides a method of fabricating a hybrid device comprised of an optical waveguide and a semiconductor device, comprising depositing two or more layers of semiconducting material onto a first substrate to form a first semiconductor stack, singulating said first semiconductor stack to form a plurality of singulated semiconductor stacks, each having an top semiconducting layer and a bottom first substrate layer, providing a second substrate having an optical waveguide deposited thereon, attaching said upper semiconducting layer of said singulated semiconductor stack to said optical waveguide to form a hybrid stack, and removing said two or more layers of semiconducting material in said second hybrid stack from said first substrate layer.
The present invention may provide the advantage of an easy transfer of single semiconductor devices from their original substrate to a second substrate. The proposed process of transferring the semiconductor devices offers an improved handling and alignment towards the second substrate of the devices. The proposed transfer method is very robust.
The present invention can provide the advantage of an improved stacking of semiconductor slices to obtain tandem solar cells.
The present invention can provide the advantage that, during the process of hybrid integration, the active side of the semiconductor element is protected and remains essentially unaffected.
The present invention can provide the advantage of re-using the original substrate after the active device is transferred to a second substrate.
The present invention provides an easy and highly accurate substrate removal, which is a large advantage for subsequent processing, and still maintains a high level of performance. In combination with the limited environmental load compared to As, this makes Ge for these specific applications a more attractive substrate material than GaAs.
The present invention combines the advantages of a good growth substrate with a high performance active microwave circuit.
The present invention can offer the advantage of combining MCM-D technology and HEMT technology yielding both high frequency devices and optical devices on the same substrate. This substrate comprises the optical waveguide forming an optical interconnect between different components or circuits or parts thereof present on this substrate.
The present invention can provide the advantage of an improved and easier stacking of semiconductor slices to obtain tandem solar cells.